Re: [PATCH 1/4] rtmutex: avoid null derefence in WARN_ON
From: Darren Hart
Date: Sat Jul 10 2010 - 10:42:54 EST
On 07/09/2010 05:29 PM, Steven Rostedt wrote:
On Fri, 2010-07-09 at 15:32 -0700, Darren Hart wrote:
If the pi_blocked_on variable is NULL, the subsequent WARN_ON's
will cause an OOPS. Only perform the susequent checks if
pi_blocked_on is valid.
Signed-off-by: Darren Hart<dvhltc@xxxxxxxxxx>
Cc: Thomas Gleixner<tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra<peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar<mingo@xxxxxxx>
Cc: Eric Dumazet<eric.dumazet@xxxxxxxxx>
Cc: John Kacur<jkacur@xxxxxxxxxx>
Cc: Steven Rostedt<rostedt@xxxxxxxxxxx>
Cc: Mike Galbraith<efault@xxxxxx>
---
kernel/rtmutex.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 23dd443..baac7d9 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -579,9 +579,10 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate)
raw_spin_lock(&pendowner->pi_lock);
- WARN_ON(!pendowner->pi_blocked_on);
- WARN_ON(pendowner->pi_blocked_on != waiter);
- WARN_ON(pendowner->pi_blocked_on->lock != lock);
+ if (!WARN_ON(!pendowner->pi_blocked_on)) {
+ WARN_ON(pendowner->pi_blocked_on != waiter);
The above actually has no issue if the pi_blocked_on is NULL.
It doesn't, but it's also redundant and makes the console noisier for no
reason. Seemed worth while to drop it under the if in the same go.
--
Darren
The below, well yeah.
-- Steve
+ WARN_ON(pendowner->pi_blocked_on->lock != lock);
+ }
pendowner->pi_blocked_on = NULL;
--
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team
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